The benefits obtained by using pulsed laser diodes with repetition rates much higher than the Doppler frequency are described and the advantages over cw&hyphen; and long&hyphen;pulse operation are shown. These benefits are achieved by several characteristics of pulsed laser operation. First, in pulsed mode the time&hyphen;averaged number of photons may be considerably higher than in cw&hyphen;mode. Second, for some of the LDA data acquisition systems the laser pulses can be synchronized with the sampl...

There are many process parameters that influence the results of laser marking of ceramic materials. Some parameters should be kept within certain tolerance limits to ensure the expected quality of the laser processing. Hence a closed loop control system may be desirable during the process for quality control. For this, an accurate multi-input and multioutput dynamic...

Over the past few years, a comprehensive rewrite of the American National Standard for Safe Use of Lasers (ANSI Z136.1) has been conducted. The ANSI Z136.1 is a user standard, as opposed to a manufacturer standard like the Federal Las...

K. WatkinsLaser Engineering Group, Department of Engineering, The University of Liverpool, Liverpool L69 3GH, United Kingdom

Slate is a natural stone which has the characteristic that shows a well-developed defoliation plane, allowing to easily split it in plates parallel to that plane which are particularly used as tiles for roof building. At present, the manufacturing of slate is mostly manual, bein...

A high-power pulsed Nd:YAG laser was employed to irradiate a 20-μm-thick Zn coating on a carbon steel surface. The ablation rate was defined as ablated volume divided by consumed laser energy, and was used to assess ablation cleaning ability. The relationships of ablation rate to laser pulse width and ablation rate to laser fluence were investigated, and optimal processing conditions were dete...

The depth of the melt layer during laser surface alloying plays a significant role in the shape of the melt pool. There appear to be critical depths at which the molten layer becomes unstable and alters its shape in response to convective flow patterns. The Marangoni number provides an understanding of the influence of the material properties on convection and subsequently the melt shape, being inversely proportional to depth squared, viscosity, and thermal diffusivity, and directly proportional to the surface t...

In laser drilling and keyhole welding, multiple reflection phenomena determine how the energy is transferred from the laser beam to the workpiece, and, most importantly, all other physics such as fluid flow, heat transfer, and the cavity shape itself depend on these phenomena. In this study, a multiple reflection model inside a self-consistent (or self-evolving) cavity has been developed based on the level set method and ray tracing t...

This article examines the particles formed during optimized laser scabbling of concrete in order to help determine an effective filtration strategy for the process. The laser scabbling technique has been developed ...

Tuning a laser wavelength to the stretching vibration of specific biomolecules has some advantages in ablating hard tissue and for surface modification induced by the photothermal or the photomechanical interaction. A tunable pulsed transversely excited atmosphere CO2 laser was tuned to 9.45 μm, which is the stretching vibration of phosphoric acid in hydroxyapatite. Dried cow dentine was irra...